The present invention relates generally to tablet dissolution testing and more particularly to a novel tablet dissolution apparatus.
In the pharmaceutical industry, it is commonplace, during pharmaceutical formulation development, stability determination, analytical development, quality control, or otherwise, to ascertain the rate at which a drug in solid form (hereinafter referred to as a "tablet") dissolves under certain well-defined conditions. In this manner, one can gauge or predict the dissolution rate of the tablet in the human stomach. Historically, tablet dissolution testing has been performed largely manually; however, recently, certain automated tablet dissolution apparatuses have been developed.
For example, in commonly-assigned U.S. Pat. No. 5,816,701, inventors Martin et al., which issued Oct. 6, 1998, and which is herein incorporated by reference, there is disclosed one such automated tablet dissolution apparatus. In a preferred embodiment, the apparatus of the aforementioned patent includes a dissolution vessel removably seated within an aluminum platen. The apparatus also includes an assembly for automatically measuring a desired volume of media, heating and degassing the volume of media and then dispensing the volume of media into the dissolution vessel. In addition, the apparatus includes a carousel having a plurality of compartments, the carousel being rotatably mounted on a stage, the stage being alignable with the vessel. According to one mode of operation, an open-top, cage-type basket is placed in one or more compartments of the carousel, each basket containing a tablet intended for dissolution. The apparatus additionally includes a shaft aligned with the vessel, the bottom end of the shaft being adapted to frictionally fit together with a basket. The shaft is rotatable and vertically movable so that it can fit together with a basket, pick the basket up out of the carousel, lower the basket into the vessel, rotate the basket within the media and remove the basket from the media. The apparatus further includes a catheter automatically movable in and out of the vessel for sampling the media at desired times, an automated mechanism for loading and replacing a depth filter on the input end of the catheter, an automated mechanism for removing the basket from the end of the shaft after testing has been completed and an automated mechanism for removing media from the vessel after testing has been completed. The apparatus also includes a paddle shaft which may be used interchangeably with the basket shaft if tablets are placed directly in the compartments of the carousel and are then dispensed from the carousel into the vessel through an opening in the bottom of each carousel that is alignable with an opening in the stage.
Although the aforementioned automated tablet dissolution apparatus works well with tablets whose dissolution is typically effected using a rotatably-driven, cage-type basket and also works well with tablets that do not float on top of the media and whose dissolution is typically effected using a rotatably-driven paddle, the above-described automated apparatus cannot be used to test tablets that float on top of the media and whose dissolution is typically effected by placing such a tablet in a weighted "sinker" and then using a rotatably-driven paddle to cause the dissolution of the tablet in the sinker. One reason why the above-described automated tablet dissolution apparatus cannot be used with tablets requiring the use of sinkers is that said apparatus is not designed for the automated retrieval of a sinker from the dissolution vessel following the testing period.
Typically, when sinkers are used with conventional non-automated testing equipment, they are retrieved manually. The present inventor is aware of one automated tablet dissolution apparatus in which a specially-designed sinker is retrieved with a robotic assembly. However, as can readily be appreciated, the aforementioned automated tablet dissolution apparatus comprising the foregoing robotic assembly is limited in its usefulness to testing those tablets for which use of the specially-designed sinker is accepted. Consequently, because certain tablets have dissolution protocols that require the use of specific sinkers, the foregoing robotic system does not have broad applicability.